Prospects for larger or more frequent earthquakes in the los angeles metropolitan region

Far too few moderate earthquakes have occurred within the Los Angeles, California, metropolitan region during the 200-year-long historic period to account for observed strain accumulation, indicating that the historic era represents either a lull between clusters of moderate earthquakes or part of a centuries-long interseismic period between much larger (moment magnitude, M(w), 7.2 to 7.6) events. Geologic slip rates and relations between moment magnitude, average coseismic slip, and rupture area show that either of these hypotheses is possible, but that the latter is the more plausible of the two. The average time between M(w) 7.2 to 7.6 earthquakes from a combination of six fault systems within the metropolitan area was estimated to be about 140 years.     

Evidence for large earthquakes in metropolitan los angeles

The Sierra Madre fault, along the southern flank of the San Gabriel Mountains in the Los Angeles region, has failed in magnitude 7.2 to 7.6 events at least twice in the past 15,000 years. Restoration of slip on the fault indicated a minimum of about 4.0 meters of slip from the most recent earthquake and suggests a total cumulative slip of about 10.5 meters for the past two prehistoric earthquakes. Large surface displacements and strong ground motions resulting from greater than magnitude 7 earthquakes within the Los Angeles region are not yet considered in most seismic hazard and risk assessments.     

The 1987 whittier narrows earthquake in the los angeles metropolitan area, california

The Whittier Narrows earthquake sequence (local magnitude, M(L) = 5.9), which caused over $358-million damage, indicates that assessments of earthquake hazards in the Los Angeles metropolitan area may be underestimated. The sequence ruptured a previously unidentified thrust fault that may be part of a large system of thrust faults that extends across the entire east-west length of the northern margin of the Los Angeles basin. Peak horizontal accelerations from the main shock, which were measured at ground level and in structures, were as high as 0.6g (where g is the acceleration of gravity at sea level) within 50 kilometers of the epicenter. The distribution of the modified Mercalli intensity VII reflects a broad north-south elongated zone of damage that is approximately centered on the main shock epicenter.     

Clouds of venus: particle size distribution measurements

Data from the Pioneer Venus cloud particle size spectrometer experiment has revealed the Venus cloud system to be a complicated mixture of particles of various chemical composition distinguishable by their multimodal size distributions. The appearance, disappearance, growth, and decay of certain size modes has aided the preliminary identification of both sulfuric acid and free sulfur cloud regions. The discovery of large particles > 30 micrometers, significant particle mass loading, and size spectral features suggest that precipitation is likely produced; a peculiar aerosol structure beneath the lowest cloud layer could be residue from a recent shower.     

京津冀都市圈生态休闲农业发展的关键问题与对策

发展生态休闲农业是缓解京津冀都市圈生态环境压力、消除区际经济社会发展水平差距的一个重要突破口。立足京津冀都市圈一体化发展的战略需求,围绕环境、社会、经济和空间4个维度阐明了生态休闲农业的功能定位体系,从生态环境保护与适度开发、环境公平利用与外部性、低碳技术创新与区际推广、产业集聚和区域品牌创建4个方面透视了生态休闲农业发展的关键问题,提出了发展生态休闲农业、促进区域分工合作、推进城乡统筹的对策建议。     

New evidence on the size and possible effects of a late pliocene oceanic asteroid impact

Debris from a late Pliocene asteroid impact is spread across at least 600 kilometers of the ocean floor in the southeast Pacific. On the basis of iridium concentrations in sediments from six deep-sea cores, the asteroid diameter was at least 0.5 kilometer; the impacting projectile may have been one of the largest in the last few million years. The stratigraphic age of this impact is the same as that inferred for the onset of Northern Hemisphere glaciation.     

Continuous plasma outflows from the edge of a solar active region as a possible source of solar wind

The Sun continuously expels a huge amount of ionized material into interplanetary space as the solar wind. Despite its influence on the heliospheric environment, the origin of the solar wind has yet to be well identified. In this paper, we report Hinode X-ray Telescope observations of a solar active region. At the edge of the active region, located adjacent to a coronal hole, a pattern of continuous outflow of soft-x-ray-emitting plasmas was identified emanating along apparently open magnetic field lines and into the upper corona. Estimates of temperature and density for the outflowing plasmas suggest a mass loss rate that amounts to approximately 1/4 of the total mass loss rate of the solar wind. These outflows may be indicative of one of the solar wind sources at the Sun.     

Nuclear sexing in a population of Congolese metropolitan newborns

In a study of 5631 Congolese newborn children, the incidence of numerical X-chromosomal anomalies was the same as was previously reported in Europe and in North America.     

基于分形理论的撂荒耕地和未撂荒耕地空间分布研究

【目的】探讨撂荒地的影响因素和空间格局,为解决撂荒问题提供参考。【方法】借助 分形理论对研究区道路、水系、居民点和不同高程、坡度、坡向范围的撂荒耕地和未撂荒耕 地的信息维数计算,并与撂荒耕地和未撂荒耕地在不同地形要素下的面积、地块百分比对 比。【结果/ 结论】撂荒耕地空间分布比未撂荒耕地的空间分布更均匀;区内撂荒耕地和未 撂荒耕地的空间格局与水系基本一致;不同高程对范围内撂荒耕地和未撂荒耕地的空间格局 不一致;坡度大于25° 的耕地最容易撂荒,且空间范围分布最集中;6°~15° 的地块最不易撂 荒,但空间格局相对较分散;阴坡的耕地撂荒现象最严重,且分布集中;未撂荒耕地不具备 明显的坡向特征。     

浙江省柑橘区域布局研究

柑橘是浙江的第一大栽培水果。文章在分析了浙江柑橘区域布局演变与现状特征的基础上,提出了浙江柑橘优势产区布局,并论述了各区的发展方向和重点,以优化柑橘区域布局,促进浙江柑橘产业的持续协调发展。     

豫西黄土丘陵区不同退耕地土壤大团聚体 的组成及其分形特征

选取退耕10年左右的乔木林、灌木林、果园、人工草地及荒地,对表层土壤大团聚体的分布、稳定性及其分形特征进行研究。结果表明,2 mm的团聚体在土壤团粒结构中占主导地位,灌木地、乔木地和荒地土壤中2~5 mm和1~2 mm团聚体含量较耕地显著提高;灌木地、乔木地、果园、草地和荒地表层土壤中5mm和2~5 mm两个粒级水稳性团聚体含量较耕地均显著提高。灌木林、乔木林、草地和荒地土壤中干筛和湿筛团聚体的平均重量直径和几何平均直径较耕地均显著增加,分维数较耕地显著降低,这4种退耕地土壤结构显著改善,果园土壤结构的改善尚不明显。团聚体分维数能较好地描述土壤团聚体的分布状况且与土壤理化性质关系密切。     

絮凝过程的分形研究进展

水体颗粒物的絮凝过程是影响污染物迁移转化的重要因素 ,已有多年的研究历史 .分形理论作为非线性数学的活跃分支 ,在絮体及絮凝这一与高度不规则结构相关联的研究中显示出很强的实用性 ,利用分形方法可以从更近于真实的角度来刻画絮体及其形成过程 .本文就国外在絮凝分形研究中的最新成果作一综述     

Earthquakes on dipping faults: the effects of broken symmetry

Dynamic simulations of earthquakes on dipping faults show asymmetric near-source ground motion caused by the asymmetric geometry of such faults. The ground motion from a thrust or reverse fault is larger than that of a normal fault by a factor of 2 or more, given identical initial stress magnitudes. The motion of the hanging wall is larger than that of the footwall in both thrust (reverse) and normal earthquakes. The asymmetry between normal and thrust (reverse) faults results from time-dependent normal stress caused by the interaction of the earthquake-generated stress field with Earth's free surface. The asymmetry between hanging wall and footwall results from the asymmetric mass and geometry on the two sides of the fault.     

西北半干旱区湿地生态系统植物群落空间分布特征研究

该文以宁夏哈巴湖自然保护区四儿滩湿地为研究对象,探讨西北干旱、半干旱区湿地-草原生态系统植物群落空间分布特征及影响群落空间分布格局的主要环境因子。外业调查选择每年的植物生长季节,从东、东北、西、西北4个方向沿着湿地-草原生境梯度布设4条样线,每条样线均超过1 km。调查内容包括植物盖度、生物量、密度、频度、高度等,以及土壤环境因子。采用TWINSPAN数量分类方法和DCA排序方法对四儿滩湿地植被进行数量分类和排序,同时进行排序轴与土壤环境因子间的秩相关分析。研究表明:研究区植被分为3个植被型14个群丛。第一组为盐生沼泽植被,以湿生、盐生植物为主,代表群丛为芦苇+盐爪爪,主要分布在湿生带;第二组为草甸植被型,以湿生、中生植物为主,代表群丛为白刺+白草群丛,主要分布在湿地-草原交错带;第三组为草原植被型,以中生、旱生的赖草+新疆猪毛菜+苦豆子群丛为主,分布在草原旱生带。秩相关分析结果表明:土壤含水量、全盐含量、土壤养分含量（全N、速效K、有机质等）均是影响植被沿湿地-草原梯度分布格局的主要环境因子;湿地 草原不同方位间植被分布格局差异的主要影响因子是地形及放牧等。此外,该文还对重要值的完善与改进进行了探讨。      

Silicon: a possible factor in bone calcification

Silicon, a relatively unknown trace element in nutritional research, has been uniquely localized in active calcification sites in young bone. Silicon increases directly with calcium at relatively low calcium concentrations and falls below the detection limit at compositions approaching hydroxyapatite. It is suggested that silicon is associated with calcium in an early stage of calcification.     

Nanoassembly of a fractal polymer: a molecular "Sierpinski hexagonal gasket"

Mathematics and art converge in the fractal forms that also abound in nature. We used molecular self-assembly to create a synthetic, nanometer-scale, Sierpinski hexagonal gasket. This nondendritic, perfectly self-similar fractal macromolecule is composed of bis-terpyridine building blocks that are bound together by coordination to 36 Ru and 6 Fe ions to form a nearly planar array of increasingly larger hexagons around a hollow center.     

陕南丘陵区县域农田土壤养分的空间分布格局

【目的】研究陕西南部丘陵区土壤养分的空间分布情况,为区域精准农业的发展提供科学依据和实践指导。【方法】2010-2011年,以陕西省镇安县为研究区,在19个镇采集农田0～20 cm 土层土样2 283个,采用地统计学并结合“GIS”技术,构建不同土壤养分的最优半方差模型,进行普通Kriging插值分析,对该地区土壤养分的空间特征进行评析。【结果】镇安县农田土壤有机质、全氮、速效氮、速效磷和速效钾,均呈中等变异强度。在空间结构上,土壤速效磷属于弱的空间相关性,有机质、速效氮和全氮表现为中等强度的空间相关性,速效钾具有强的空间相关性。总体来看,农田土壤养分空间呈中间低、四周高的分布格局。农田土壤有机质和全氮平均含量分别为18.27,1.09 g/kg,速效氮、速效磷、速效钾平均含量分别为97.47,16.27,122.09 mg/kg。与20世纪80年代相比,2011年镇安县土壤有机质、全氮、速效氮、速效磷、速效钾的增幅分别为40.54%,17.20%,57.21%,125.97%和47.10%。镇安县土壤碳氮比平均为9.84,速效氮磷比平均为4.00。【结论】镇安县农田土壤有机质、全氮和速效磷含量处于中等水平,速效氮和速效钾含量处于中等偏上水平。土壤碳氮比较全国农田偏低,速效氮磷比整体上偏高,比例严重失调。因此,镇安县的农田应科学、合理施肥,以提高肥料利用率。